Apparatus for casting thin-walled cast iron parts



May 9, 1967 D E. GROTEKE ETAL 3,318,370

APPARATUS FOR CASTING THIN-WALLED CAST IRON PARTS 1964 2 SheetsSheet 1INVENTORS Daniel E. Groteke James A. Stovrolukis BY (11 MM ATTORN EY y9, 1967 D. E. GROTEKE ETAL APPARATUS FOR CASTING THIN-WALLED CAST IRONPARTS 2 SheetsSheet 2 Filed July 1964 s z w INVENTORS Daniel E. GrofekeJames A. Sfovrolokis BY (MM ATTORN EY United States Patent 3,318,370APPARATUS FOR (IASTING THIN-WALLED CAST IRON PARTS Daniel E. Groteke andJames A. Stavrolakis, Louisville,

Ky., assignors to American Radiator & Standard Sanitary Corporation, NewYork, N.Y., a corporation of Delaware Filed July 2, 1964, Ser. No.379,919 3 Claims. (Cl. 164-306) This invention relates to a permanentcasting apparatus suitable for carrying out the claimed process.

It is already known in the art in which this invention is classifiedthat the difiiculty of obtaining acceptable castings increases as thecross sectional area of the casting decreases. In particular, theoccurrence of holes, as caused by misruns, slag, and sand, inthin-walled castings is far more frequent and far more serious, sincesuch castings as sinks and bathtubs are to be enameled.

Various techniques have been suggested and tried in order to obtainsatisfactory thin-walled castings. Each of these suggestions have singlysuffered from one or more serious disadvantage. Thus, using regularpermanent mold practices, non-uniform temperature gradients in thesolidifying casting cause warping and distortion. Use of a thick coatingof mold wash in the female mold, as performed in the art, results oftenin a roughened casting surface. Similarly, the use of pressure alone onthe metal during or after its entry in the mold frequently has beenfound to produce unduly porous castings owing to the air or other gasesbeing entrapped in the molten metal.

The main object of this invention is to provide an automated process forformation of light, strong, uniform, thin-walled fixtures which processproduces castings requiring a minimum of secondary operations prior toenameling.

Another object of the invention is to provide a novel hydraulicallyoperated mold which is easily automated and which when operatedaccording to the method of the invention produces gray iron castings ofunusually low section thickness with little or no scrap loss.

A further object of this invention is to provide a method of producingthin-walled castings of metal characterized by pouring a molten grayiron composition into an insulated, coated, preheated female die,rapidly closing the mold by bringing the insulated preheated male die toa point just above the molten iron, slowly advancing the male die duringforming and quick opening the mold while the metal is at red heat.

Another object of the invention is to provide novel means for conveyingmolten iron in a furnace through a heated snorkel tube to a female die.

A further object of the invention is to provide novel means forextending the life of the snorkel tube by minimizing thermal shock.

These and other related objects, features and advantages of the presentinvention will be more fully understood as the description of theinvention proceeds, particularly when taken together with theaccompanying drawing in which FIG. 1 is a vertical sectional elevationof the novel forming apparatus of the invention. FIG. 2A is a circuitdiagram of a hydraulic circuit for operating said apparatus. FIG. 2B isa circuit diagram for said apparatus.

As a preferred embodiment of the invention there has been selectedapparatus suitable for the casting of bathtubs or sinks. It should beunderstood, however, that the present invention is in no way limited tothe casting of such shapes.

Referring now to the drawing, the novel forming apparatus of theinvention comprises a male die 3 (cope) which is so maneuvered forexample, by a piston in a cylinder such as shown in FIGS. 2A and 23,that at the start of any given cycle it is in open position 2; and afemale die (drag) mounted above a pressurized melting furnace 14connected therewith by a snorkel tube 6, made of a refractory alloy orcompound. Furnace 14 has a gas-tight lid 20. An auxiliary heat source 7surrounds the upper part of tube 6. This tube can be cooled if needed bypassing water which enters a cooling coil at 8 and exits at 10. Thediameter of snorkel tube 6 is such as to enable it to receive the coreprojection 11 on male die 3.

Provision is made to cool both the male and female dies by passing air,steam, or water through passages 13.

An inert gas which is non-oxidizing under the ambient conditions ismaintained over the molten metal in the furnace. Suitable inert gasesfor the purposes of this invention include nitrogen, argon, helium,chlorine or carbon dioxide. be used to convey the selected gas to thefurnace.

The method of the invention can be illustrated by referring to theoperation of the above described apparatus.

At the start of any given forming cycle, the gas pressure P over themetal in the furnace is higher than the outside atmospheric pressure.This value is suflicient to keep a column of molten metal in the snorkeltube 6 above the heat source. The pressure then is increased to a valuehigh enough to force metal up into the female die in an amountsufiicient to give a full casting with .minimal excess. This amount isdenoted in the drawing by fill line 1 while the necessary pressure maybe denoted by P The level of the fill metal and the volume of theoverflow trap are balanced to insure that all overflow metal, afterforming, is still connected to the casting by a parting line flash whichis sheared from the finished casting in a secondary trimming operation.The level of the metal in the mold is controlled by the duration andvalue of the fill pressure. The desired height of the metal is afunction of the volume of the overflow trap which is controlled by thedesign and size of the part being press formed.

While this prefill operation takes place by increasing the gas pressure,the male die may either be in position 2, which it has reached uponcompletion of the previous cycle; or at a point just above the metalfill line or in position 4. However, if position 4 is used, theinsulating value of the coating on the dies must be high enough topermit filling the casting before solidification occurs. To form thecasting, the male die (cope) is slowly brought into the female mold(drag) to the extent that the central core projection penetrates thecentral opening 16 in the female mold and displaces the molten metal tothe shape defined by the dies when closed. As soon as solidification iscomplete, the pressure is restored to P to permit the level of themolten metal to fall to the level denoted by reference character 12before opening the mold. The life of the snorkel tube is thus extendedby minimizing ther-- mal shock.

When the metal level has returned to the level indicated by 12, the maledie is quickly retracted to position 2. The press-formed casting willthen either remain in the female die or will adhere to the male die.This position can be controlled by regulating the die temperatures, thesurface finish of the dies and the cycle timing. Die temperature iscontrolled by adjusting cycle time. For example, lengthening the time amold remains closed lowers the temperature of the press formed part andincreases its shrinkage. The cast section then locks onto the cope sideof the die assembly. The preferred method is to open the mold when thecasting is between 1750 and 1500 F. The casting remains in the drag sideof the mold and is easily removed without any danger of cracking. CycleAny means well known in the art can the four-way valve.

time is a function of metal volume poured, cooling used, etc.

The finished casting can be removed by ejection off the male die withejection pins or by picking up the casting from the female mold with aconventional vacuum holder. Preferably the casting should be retractedfrom the mold before it has cooled below black heat.

All the die surfaces which are wet by the molten metal should be coatedwith either lampblack, or, preferably by a multilayer coating disclosedand claimed in co-pending Ser. No. 380,047 filed this day, now PatentNo. 3,266,- 107. The coating described in said application consists of abase coating of a high conductivity, high ductility material usedin thebase layer, an inert refractory metal oxide and a plasma-sprayedoverlayer of refractory oxide.

The apparatus of the invention may be automated by the .use of ahydraulic system controlled by an electrical circuit such asshown inFIGS. 2A and 2B, as will appear hereinafter.

In order to begin a cycle on the machine of the invention, a startswitch shown in FIG..2B is closed to pull in a hold relay, CR-l.Solenoid 1 is also energized, thereby permitting water flow through thefour-way valve into the top 40.0f the cylinder, the rod 41 isoperatively connected to male die 3.

When the cylinder starts its stroke downward, a limit switch LS-l shownin FIG. 2A, closes to complete the hold circuit, allowing the startswitch to be released.

At a point above the molten metal, the descending upper die closes limitswitch 'LS-2, energizing solenoid 3, which stops the direct exhaust ofwater from the bottom of the cylinder to the drain. Instead, the exhaustwater is channeled through the variable flow control valve. Limit switchLS'2 also energizes a timer motor and clutch, connected as shown in FIG.2B. 7 After the desired time interval is completed, the timer switchTM-l closes, energizing solenoid 2, which changes This provides free,fiow of water through the check valve into the bottom cylinder. Waterexhausting from the top is directed to the drain.

As the piston starts to retract, LS2 is opened. 'Atthe topv of .thereturn stroke, the normally closed 0 limit switch; LS.1 -opens, the holdrelay, timer clutch,

and motor drop out, solenoid 1 is deenergized and all motion ceases.

In successful demonstrations of the practice of the ini vention, thedies of the machine shown in FIG. 1 were maintained at a temperature of700 to 800 F. and the "metal pouring temperature between 2400 and 2750F.

7 I shapes was excellent.

Having thus described and explained this invention and its mode ofoperation it will be understood that numerous variations in the form andarrangement of parts shown and described may be made without departingfrom the nature and scope of the invention, except as defined in theappended claims.

What is claimed is:

1. In an apparatus for press-forming thin walled cast iron parts, andhaving;

(a) a gas tight, pressurized holding furnace, having an opening in thetop portion thereof;

(b) a snorkel tube mounted on said holding furnace, and extending intomolten metal in said furnace;

(c) a female die mounted above said snorkel tube and having an openingin operative communication with said snorkel tube;

(d) a male mold mounted proximate said female die, said female die andsaid male mold being spaced apart so as to provide a mold cavity; I

(e) means. to selectively increase and decrease the gas pressure withinsaid hold furnace and thereby force,

molten metal from said furnace, upward-1y through said snorkel tube andinto said mold cavity;

(f) means to cause molten metal in said mold cavity to cool andsolidify, the improvement comprising:

said male mold having a central core projection positionso as to projectthrough said opening in said female die and below the level to whichmolten metal solidifies, and heating means to heat the molten metalwithin said snorkel tube and maintain the upper level of the'molten ironabove the bottom of the said central core projection during the moldingoperation, whereby decreasing the pressure in said holding furnace aftersolidification of the metal in said mold cavity causes the level of themolten metal to drop from a point above the bottom of said coreprojection to a point below the bottom of said core projection.

2. The apparatus of claim 1, wherein cooling means are provided formaintaining said core projection within desired operating limits.

3. The apparatus of claim 1, further comprising a cylinder connected tosaid male die and adapted to move the same in relation to said femaledie, a hydraulic circuit for actuating said cylinder, electric means forcontrolling said hydraulic circuit, said means including means forenergizing said hydraulic system, means for holding said systemstationary, and means for de-energizing the same.

References Cited by the Examiner J. SPENCER OVERHOLSER, PrimaryExaminer.

R. SPENCER ANNEAR, Assistant Examiner.

1. IN AN APPARATUS FOR PRESS-FORMING THIN WALLED CAST IRON PARTS, ANDHAVING; (A) A GAS TIGHT, PRESSURIZED HOLDING FURNACE, HAVING AN OPENINGIN THE TOP PORTION THEREOF; (B) A SNORKEL TUBE MOUNTED ON SAID HOLDINGFURNACE, AND EXTENDING INTO MOLTEN METAL IN SAID FURNACE; (C) A FEMALEDIE MOUNTED ABOVE SAID SNORKEL TUBE AND HAVING AN OPENING IN OPERATIVECOMMUNICATION WITH SAID SNORKEL TUBE; (D) A MALE MOLD MOUNTED PROXIMATESAID FEMALE DIE, SAID FEMALE DIE AND SAID MALE MOLD BEING SPACED APARTSO AS TO PROVIDE A MOLD CAVITY; (E) MEANS TO SELECTIVELY INCREASE ANDDECREASE THE GAS PRESSURE WITHIN SAID HOLD FURNACE AND THEREBY FORCEMOLTEN METAL FROM SAID FURNACE, UPWARDLY THROUGH SAID SNORKEL TUBE ANDINTO SAID MOLD CAVITY; (F) MEANS TO CAUSE MOLTEN METAL IN SAID MOLDCAVITY TO COOL AND SOLIDIFY, THE IMPROVEMENT COMPRISING: SAID MALE MOLDHAVING A CENTRAL CORE PROJECTION POSITION SO AS TO PROJECT THROUGH SAIDOPENING IN SAID FEMALE DIE AND BELOW THE LEVEL TO WHICH MOLTEN METALSOLIDIFIES, AND HEATING MEANS TO